1. Field of the Invention
The present invention relates to a substrate treatment apparatus for performing treatment on a substrate.
2. Description of the Related Art
In a photolithography process in a manufacturing process of a semiconductor device, a series of treatments including a resist coating treatment, an exposing treatment, and a developing treatment are performed, for example. In the resist coating treatment, a resist solution is applied to a wafer to form a resist film. In the exposing treatment, the resist film is exposed to have a predetermined circuit pattern. In the developing treatment, the exposed resist film is developed. Thus, a predetermined resist pattern is formed on the wafer. The series of treatments are performed in a coating/developing apparatus to which various kinds of treatment units for performing treatments on a wafer, a carrying apparatus for carrying the wafer, and the like are provided.
Generally, the coating/developing apparatus includes a cassette station, a treatment station, and an interface station. The cassette station is used for carrying a cassette into/from outside. To the treatment station, a plurality of treatment units for performing various kinds of treatments such as the resist coating treatment, the developing treatment, and a heat treatment are provided. Through the interface station, a wafer is delivered/received between an adjacent exposing apparatus and the treatment station.
On the cassette station, a cassette loading table on which a cassette externally carried in is loaded, a wafer carrying apparatus for carrying a wafer between the cassette on the cassette loading table and the treatment station, and the like are provided (see, Japanese Patent Application Laid-open No. 2006-54438).
In performing a treatment on a wafer in the coating/developing apparatus, first, a cassette that contains a plurality of wafers of one lot is loaded on the cassette loading table by an external cassette carrying apparatus. Next, the wafers in the cassette are sequentially carried to the treatment station by the wafer carrying apparatus. In the treatment station, the wafers are sequentially carried to the plurality of treatment units such as the resist coating unit and the heat treatment unit to be subjected to predetermined treatments. After that, the wafers are carried to the exposing apparatus and subjected to exposure. Then, the wafers are returned to the treatment station and sequentially carried to the developing treatment unit, the heat treatment unit, and the like to be subjected to predetermined treatments. The wafers that have been subjected to the series of treatments in the treatment station are sequentially returned to the original cassette on the cassette loading table by the wafer carrying apparatus. When all the wafers of one lot are returned to the cassette on the cassette loading table, the cassette is carried out of the coating/developing apparatus by the external cassette carrying apparatus.
Incidentally, these days, the coating/developing apparatus is being required to deal with a so-called small-lot treatment in response to a change to a low-volume production of diversified products. In the case of the small-lot treatment, the number of wafers contained in one cassette is reduced. For this reason, when wafer treatments are started, the wafers in the cassette on the cassette loading table are immediately ejected in many cases. However, the cassette stands by on the cassette loading table until the wafers are returned from the treatment station, so an additional cassette cannot be loaded on the cassette loading table, although there is an open space for the wafer treatment in the treatment station. As a result, a throughput in the coating/developing apparatus is lowered.
In this case, as a simple countermeasure, the number of cassettes that can be loaded on the loading table may be increased. However, this results in an increase in occupied floor area of the coating/developing apparatus, and requires a structure of the cassette station to be significantly changed.